Process for making styrene and substituted styrenes



Patented Sept. 20, 1949 PROCESS FOR MAKING STYRENE AND SUBSTITUTED STYRENES William M. Quattlebaum, Jr., Charleston, W. Va.,

assignor to Carbide and Carbon Chemicals Corporation, a corporation of New York No Drawing. Application July 9, 1946, Serial No. 682,297

8 Claims.

In the copending application, Serial No. 458,736, filed September 17, 1942 by me and W. J. Toussaint, entitled Process for making olefines, now Patent No. 2,407,291 we have shown that carbonyl compounds capable of keto-enol tautomerism are deoxygenated to the Corresponding olefines when they are passed over a silica gel catalyst together with an alcohol capable of dehydrogenation to a carbonyl compound, the alcohol being simultaneously reduced to an aldehyde or ketone. In our previous joint application, we specifically applied this reaction to the production of monoand diolefines, including the formation of butadiene from crotonaldehyde and ethanol, but we also demonstrated that styrene could be formed from acetophenone and ethanol by this reaction. In our copending application, Serial No. 682,298, filed simultaneously herewith, as a continuation-in-part of our joint application Serial No. 458,736, we claim the process of making styrene and its derivatives from acetophenone, or its derivatives, and alcohols in the presence of silica gel. Although silica gel is the preferred catalyst for this reaction, I have found that acetophenone and substituted acetophenones can be converted to styrene and substituted styrenes in the presence of a certain class of catalysts. This finding was made independently of our joint discovery of the outstanding effectiveness of silica gel as a catalyst for the same reaction.

According to the present invention, acetophenone and substituted acetophenones, such as the chloroacetophenones, together with primary or secondary alcohols, are passed over dehydratingdehydrogenating catalysts, to form styrene or substituted styrenes, such as the chlorostyrenes, by a deoxygenation reaction. By a dehydratingdehydrogenating catalyst is meant a catalyst capable of both dehydrating and dehydrogenating ethanol vapors at elevated temperatures of about 300 to 400 C. to form gas mixtures containing at least some hydrogen and at least some ethylene. Materials which give only ethylene from ethanol, such as thorium oxide, ThO-z, are excluded because they are wholly ineffective as catalysts for the present reaction. For similar reasons, materials which give only hydrogen from ethanol, such as tin oxide, SnOz, are also excluded. In general, the present classification of dehydrating-dehydrogenating catalysts follows that of Sabatier; see Rideal and Taylor Catalysis in;

Theory and Practice" p. 356-357 (1926) and Sabatier, Catalysis in Organic Chemistry," p. 252 (1923). However, materials, such as alumine, are herein considered to be dehydratingdehydrogenating catalysts because they do not have a dehydrating action exclusively according to Sabatiers tests.

' Dehydrating-dehydrogenating catalysts other than silica gel which are effective catalysts for the present deoxygenation reaction include alumina, titania, zirconia, molybdenum oxide, tantalum oxide and magnesium silicate. Some of these catalysts,such as alumina gel, silica gel and magnesium silicate may be obtained commercially, and others may be prepared according to known methods. For instance, catalysts composed of metal oxides supported on inert carriers may be prepared according to Graver, U. S. Patent No. 1,914,558.

The deoxygenation reaction of this invention may be illustrated by the following general equation:

phenone compound where R is an aromatic radical having a single benzenoid ring, R1 is an alkyl radical and R2 is hydrogen or an alkyl radical. As examples of acetophenones may be mentioned acetophenone, ortho, meta, and para chloroacetophenone, the various dichloroacetophenones, the trichloroacetophenones, ortho, meta and para methyl acetophenone, and the various dimethyl acetophenones. Any of the typical primary or secondary aliphatic alcoholsmay be utilized. in the deoxygenation reaction, such as ethanol, isopropanol, butanol, secondary butyl alcohol, pentanol, hexanol and the like. In general, it is preferable to employ a substantial molar excess of the alcohol, for instance three to nine moles of the alcohol per mole of the acetophenone. After passage over the catalyst, the unchanged alcohol may be recovered and recycled. Most of the alcohol consumed is converted to the corresponding carbonyl compound, which is usually more valuable than the alcohol. If not, the carbonyl compound can be easily hydrogenated to form the alcohol. Very little alcohol is lost by dehydration to an olefine, although secondary alcohols are somewhat more easily dehydrated than primary alcohols.

It is not essential to use pure acetophenones in the deoxygenation reaction. Mixtures of acetophenones and the corresponding aromatic aloohols, such as may be obtained by oxidizing ethyltures being 300 to 400 C. In general, the yield increases with the temperature employed, but it is preferable to operate at temperatures lower than those at which the maximum yield is obtainable, as shown in the examples, in order to avoid side-reactions and to increase the efiiciency. of the process. The time of contact of the res actants with the catalyst may be varied, but, as a rule, a feed rate of 0.5 to 1.5 volumes of liquid reactants per volume of catalyst per hour is suit-. able. The reactants are, of course, vaporized before they pass over the catalyst. Thus,"the' time of contact of the reactant vapors with-the cataeilyst may be about 1 to 4 seconds.-- a 1 The following procedure was followed in carry i ing out the deoxygenation reactions of the spe- General procedure The reaction chamber consisted of a vertical,

one-inch, s'tainle'ss' steel -i tube 1 in which 300. c; c. of the catalyst of suitable particle size. usually 4 x 8 mesh, were placed. The catalystsee'mployed were commercial types-"except the supported metal oxides which were prepared according to Examples 7, 20 and 22 of'Craver U. S; Patent No. 1,914 558. The reaction .zone was. preceded by a preheating section containing 150'. c.1c of Filtrosjan inert formof silica. j The reaction tube was heated by means of-a jacket containing a heating fluid.

Instartinga run thetemperature. of the catalyst bed was raised slowly, commencing at about 25.0? 0., while a mixture;oithelacetophenone and the alcohol was introduced usuallyat'a rateof about 300 cs'c. of iliquidperhour at; the top of the'tube. The vapors emerging at the bottom of the tube were condensed, and a sample of-the product titrated at intervals to determine the amount of unsaturation, and hence the amount of reaction. :When a'temperaturev was reached at which a good conversion to the styrene compound wasindicated. the run was continued at Example 3.Sty rene-molybdenum oaiide A-mixtur e of 720 grams; of acetophenone and 1175 grams of; ethanol containing small amounts of water and acetaldehyde were vaporized at the rateof 300 c. c. of liquid per hour and the vapors were .passedover 300 c. c. of' molybdenum oxide supported on Filtros maintained at 350 C.

Styrene was obtained under these conditions in a wieldof 9% andat an efi'iciency of 78%.

this temperature, using 'fweighed "amounts of A starting materials. Theproduct formed; during the quantitative part of the 'ru'n'WasTCOIIeQted and carefully analyzed bydistillation. v7 Example 1. -Sty1 eae-magaesium silicate A mixtureof 720 grams of acetophenone and 1175 grams of ethanol containing small amounts of water (about 7%.) and acetaldehyde, (about 1% was vaporized at the rate. of 300 c. c. of liquid per hour. The vapors were passed over 30.0 c. c. of commercial magnesium silicatepel-v lets at 300 C. The product wasdistilledthrough a highly eflicient rectif -yingcolumn which made possible the removalof anethanol fractioncon taming only a small amount of styrene, Atotal of 194 grams of styrene (including. that inthe ethanol fraction) was obtained, and 392: grams of acetophenonefwere recovered. The yield and efficiency were thus-31% and 68% respectively.

7 The efficiency is definedas the ratio oithe moles:

of acetophenone converted to; styr'eneto the total moles of acetophenone reacted. 'lfhe purity V of the styrene was-9'7%. a l,

Example 2.jS'tyrene-zirconium oicide i A' mixture of the same composition as one used in Example 1 was% vaporizedat thev rateof 300 c. c. of liquid-per hour and the-vapors passed 0ve'r..300. c. c. of zirconium oecide'supported on V The temperature; employed was 350 V More ethanol was dehydrated to ethylene than oc *curred with the catalysts of the previous examples. The purity of the styrenewas greaterthan 'Eazample 4.-Styrene-tantalum oxide 'Ain'ixture of the same composition as used in Example 3 was passedat the same space velocity over tantalum oxide supported-fen Filtros maintained at 300 C. Styrenerof 99% purity was-obtained ima yield of 1.8% andat'anefii ciencyof'62%-. Eaample 5 M0aochlorosiyrene tantalum oxide Six gram-moles of monochlorophenyl methyl ketone and 24 gram-moIes ofethanolcontaining small amounts of Water and -=acetaldehyde 'rwer'e vaporized at the rate -of 295 0.- c} of liquidper hour.. The vaporsw'ere conducted even 300 etc; of tantalumoxide 'supported cn--Filtrcs. -The temperature was held-at 350 9:- -'-Uponrectification of the produetin' the usual-wane 26% yield of chlorostyreneof high purity -was'-obtained,-with an efficiency basedon chlorophenyl-methyl ketoneof-84%. I

,, To fildigrams of "monochlorophenyl methyl kes 7 tone was ,addedllflfi .gramsioftethanolcontaim ing small amounts of. :w'ater. and acetaldehyde;

This mixturawhichhadjamolanratio of ethanolto lgetone ofapproximately 6 magmas-vaporized atthe rateeof 310 0.:c. ofliquidper; hour'and the vaporsled over 300 each of commercialcalumina gel maintained at. a temperature-of 350?- C. Distillation oi the product-wielded 46:1. grams' bi chlorostyrene higher in; purity than 98%. o The o e on undenthesecenditiom was so high that some Icy-products were formed and little unreacted ketorle was. recovered. The yield was 82%. of the theoretical amounts... 1

Example nmtocmeoeta a am raze The procedure of Example 6 was followed using for producing styreneand its derivatives for this purpose since the mono'mers are'ef high purity;

The deoxygenajtion reaetion'fisa particularlyusef.ul= reaction for producing-"the *chlorosty'renes since these materials are d-i fiicultto prepareby the usual methods whieh ai e-einployed for-producing styrene. These methods'T-ii volve the hydrogenaw' 1 tionof' acetoph'enone' and subs p J V ent dehydration of p n-yl methylearbincl tion-of ethylbenzene.- 'The 'i ormerj-processkis net suitable 1 converting clileroacetcphenones to The a me-eta;

chlorostyrenes because the hydrogenation catalysts employed in the hydrogenation step become poisoned. The dehydrogenation of ethylchlorobenzenes is not a satisfactory process because it is extremely diflicult to separate the chlorostyrenes from the ethylchlorobenzenes. This is because isomers are present, the materials to be separated differ only slightly in boiling points, and the chlorostyrenes polymerize readily during distillation. With regard to the preparation of styrene from acetophenone, the present process has the advantage that it eliminates the hydrogenation step.

Modifications of the invention, other than as described in the specific examples, may be made without departing from the scope of the invention as defined in the appended claims.

I claim:

1. Process for making a styrene compound of the group consisting of styrene and chlorostyrenes .-1

which comprises passing the vapors of one of the group consisting of acetophenone and ring-substituted chloroacetophenones and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to nine moles of the alcohol per mole of the acetophenone compound over a dehydrating-dehydrogenating catalyst at an elevated temperature, and recovering from the reaction products a styrene compound and an aliphatic carbonyl compound :3

corresponding to the dehydrogenation product of said alcohol.

2. Process for making styrene which comprises passing the vapors of acetophenone and an aliphatic monohydric alcohol capable of dehydrocomprises passing the vapors of a ring-substituted chloroacetophenone and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to nine moles of the alcohol per mole of the chloroacetophenone over a dehydrating-dehydrogenating catalyst at a temperature of about 200 to about 500 C., and recovering from the reaction products a chlorostyrene and an aliphatic carbonyl compound corresponding to the dehydrogenation product of said alcohol.

4. Process for making a monochlorostyrene which comprises passing vapors of a ring-substituted monochloroacetophenone and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to nine moles of the alcohol per mole of the monochloroacetophenone over a dehydrating-dehydrogenating catalyst at a temperature of about 200 to about 500 C., and recovering from the reaction products a monochlorostyrene and an aliphatic carbonyl compound corresponding to the dehydrogenation product of said alcohol.

5. Process for making a styrene compound of the group consisting of styrene and chlorostyrenes which comprises passing the vapors of one of the group consisting of acetophenone and ring-substituted chloroacetophenones and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to nine moles of the alcohol per mole of the acetophenone compound over a catalyst comprising tantalum oxide at a temperature, of about 200 to 500 C. and recovering from the reaction products a styrene compound and an aliphatic carbonyl compound corresponding to the dehydrogenation product of said alcohol.

6. Process for making a styrene compound of the group consisting of styrene and chlorostyrenes which comprises passing the vapors of one of the group consisting of acetophenone and ring-substituted chloroacetophenones and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to nine moles of the alcohol per mole of the acetophenone compound over a catalyst comprising zirconium oxide at a, temperature of about 200 to about 500 C., and recovering from the reaction products a styrene compound and an aliphatic carbonyl compound corresponding to the dehydrogenation product of said alcohol.

7. Process for makin a styrene compound of the group consisting of styrene and chlorostyrenes which comprises passing the vapors of one of the group consisting of acetophenone and ring-substituted chloroacetophenones and an aliphatic monohydric alcohol capable of dehydrogenation to a carbonyl compound in the ratio of three to n ne moles of the alcohol per mole of the acetophenone compound over a catalyst comprising magnesium silicate at an elevated temperature, and recovering from the reaction products a styrene compound and an aliphatic carbonyl compound corresponding to the dehydrogenation product of said alcohol.

8. Process for making a cholorstyrene which comprises passing the vapors of a ring-substituted chloroacetophenone and ethanol in the ratio of three to nine moles of ethanol per mole of the chloroacetophenone over a catalyst comprising tantalum oxide at a temperature of about 300 to about 400 C., and recovering from the reaction products a chlorostyrene and acetaldehyde.

WILLIAM M. QUATTLEBAUM, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,877,203 Schoeller et al Sept. 13, 1932 2,204,978 Bartlett June 18, 1940 2,407,291 Quattlebaum et a1. Sept. 10, 1946 2,421,361 Toussaint et al. May 27, 1947 2,423,681 Butterbaugh et al. July 8, 1947 FOREIGN PATENTS Number Country Date 538,353 Great Britain July 31, 1941 OTHER REFERENCES Sabatier et al., Bull. de la Soc. Chim. Ser. 4, vol. 15, 227 (1914). 

